Sea,
I tried to write something before - but I was afraid you might take it in the wrong light; that it would just add pain. I don't want to do that, so please understand that I'm trying to help - not hurt. I'm not sure I could've taken it that way, when I was in your shoes, either.
There is another way to see this situation than just an either/or choice by your D... that leaves you feeling rejected for the ex who you know beyond a shadow of a doubt, is a hurtful and dangerous person. Your D is an adult now and she deserves the opportunity to get to know her father, make her own assessments of him, decide for herself... without feeling the need to "choose" one parent over the other. I say that from my experience of being a D in that position. You can trust that eventually he'll "out" himself. Ns always do. She might get hurt, herself... true. But if you don't shut her out of your heart, you can help comfort her and help her understand the "tricks of the N game" later. (My situation with my mom is quite different than this.)
As a mom, I have two experiences that shared, might be able to shed some light on your own experience. I let my D's live with my Ex, while they were still young. Because of my experience, having to "choose" one parent over the other, I felt an obligation to not deny them the opportunity to have a relationship with him. It didn't turn out well, I have to say. But we all lived through it and have gotten past it. I felt like a miserable failure as a mother at the time. Selfish as all get out, too. Guilty beyond belief. Hurt to the core of my being. Like you are feeling now, I felt they "chose" him over me. But that was just my feeling - it wasn't what was really taking place. All's well that ends well, right? We're still working on the "happy ending" but the fact is, both girls are stronger people for having been allowed the chance to explore, discover, and maintain their own boundaries with both of us and create a version of a relationship with him -- to care about him in their own way and establish their own boundaries with him without feeling responsible for me and how I feel; as if I'm going to fall apart because of it.
My girls are in their early 30's now; that all happened 20 years ago. One of the things I struggled with in T, was redefining what my role as "mom" consisted of now. Just like when they were little - each relationship is slightly different and each has their own sensitive zones, boundaries, etc. I needed to learn how to not "need to be needed" by my Ds... they weren't children anymore... our relationship, how we interacted, hadn't grown and evolved over time. I was stuck... and not letting go. And I felt like my whole identity would go up in a puff of smoke... if I wasn't the same old mom anymore. Once I started to shift my focus to taking care of me, instead of 24/7 worrying and ruminating about them... things changed for the better pretty quickly. And the interesting thing is, that it seems that some new "space" opened up for our relationship to change and grow, too. Their lives also started to seek a balance.
What they do with their Dad and how they feel about him -- is none of my business. The freedom they've had to connect with him, get to know him, make their own kind of peace between us - for themselves... has actually helped them understand why I divorced him in the first place. And it's helped them to grow some compassion, wisdom, and understanding that they can apply in their own relationships, too. And now, I think the girls and I are closer than ever... they don't need the "old mom"... and I've changed a bit... and they've grown... and we're still friends and enjoy being with each other.
I guess, this is my version of the "middle path", Sea. Yours will probably be a different combination... I do think, though, that no matter the age of the child, it's absolutely important to not see the situation in terms of choosing one parent over the other... even if those words are actually spoken... because later on, your D might see things quite differently than now. So, in the meantime, focus on you... and your life... and who you are now... and who you want to be in a year, 10, etc. It's the great gift of freedom, after single-momming for years... even though it might not feel like it inititally. It will be all right, Sea.
(((((((((((SEA)))))))))))))))